[sdiy] Hard Sync on DCOs

[Richie Burnett]

> Given that it is easy enough to make a hard sync sound on a DCO by 
> including a reset comparator as well
> as the uPs reset pulses and simply ORing the two sets of reset pulses 
> together (allowing you to boost the
> DCO amplitude compensation CV to produce sync bend), would anyone care to 
> speculate why more DCO
> synths don't/didn't do this?

The JX-3P and JX-8P both offered oscillator hard sync on their DCOs from 
what I remember.

I seemed to remember that the sync on the JX-3P was quite strange though.  I 
think a sync'd sawtooth waveform starts again from half-way up the ramp 
where it's value crosses zero, rather than starting right from the very 
bottom of the ramp when reset like most synths.  Maybe this was done to 
minimise DC offset in the output of a sync'd oscillator, I don't know.  It 
definitely sounded different to a usual hard sync'd sawtooth.  You could 
think of it as the difference between hard syncing a cosine wave vs a sine 
wave.  They reset back to different places in the cycle.

-Richie,